1. Field of the Invention
The present invention relates to an apparatus for monitoring torsional vibration of a rotating shaft system for such as turbine generator, in which torsional vibrations produced in the rotating shaft system are measured at measurable positions thereof and the measured vibrations are decomposed linearly to estimate torsional vibration at an arbitrary position of the rotating shaft system and thereby monitor the rotating shaft system.
2. Description of the Prior Art
It has been commonly recognized that, in designing a rotating shaft system such as turbine generator, compressor or marine diesel engine, it is important to know exactly various disturbances affecting the rotating shaft system. Particularly, it is very important for operators of the rotating shaft system to know the fatigue life expenditure of the rotating shaft system which may vary with the disturbances.
Since, however, the length of the rotating shaft system of, for example, the turbine generator is generally very long and may become several tens of meters in some cases, it is necessary to set a number of measuring positions along the rotating shaft system. This makes monitoring of the shaft system very difficult. Furthermore, it is well known that torsional vibrations occurring along the rotating shaft system must be measured because such vibrations may fatigue and damages the shaft system. However, it is disadvantageous economically to install torsional vibration measuring devices at a large number of positions on and along the rotating shaft system and it is sometimes impossible physically to do so.